Running rough
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Running rough
I recently purchased a Cerry 1994 F-150 short box with a 302. It runs rough at idle up past 300 rpm. My mechanic has check everything he can think of, replaced the plugs and wires as well as the pvc valve. It says it has a vacuum leak but he can't find it. any experience or advice out there?
Lead Driver
Joined: Nov 2002
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From: Concord, NC
Are there any error codes in the computer? You can check them yourself - go to http://fordfuelinjection.com and click on "Getting Codes" if you are unfamiliar with the process.
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From: Memphis, TN USA
To locate some vacuum leak, spray some carb cleaner around the intake gaskets and around manifold and its gaskets as well as the carb base gaskets. If you found the leak and you have sprayed it then it will change your IDLE and the RPM will change.
You may have to disconnect other vacuum hoses temporarily and plug it up and see if the IDLE RPM changes. Candidates are brake booster vacuum hose, cruise control servo vacuum hose, Air/Vent vacuum actuator hose, PVC hose etc. Just try to plug them up and see if the IDLE RPM changes and you can narrow down a leaking hose.
You may have to disconnect other vacuum hoses temporarily and plug it up and see if the IDLE RPM changes. Candidates are brake booster vacuum hose, cruise control servo vacuum hose, Air/Vent vacuum actuator hose, PVC hose etc. Just try to plug them up and see if the IDLE RPM changes and you can narrow down a leaking hose.
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From: Ashland City, TN
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Running Rough -update
You guys are pureists! When you been doing building construction for 28 years, PVC and PCV are easy to mix up. Just like GFCI and GFI and now AFCI. Anyway, I tried the injector cleaner and sprayed some carb cleaner aroound on the intake but nothing has changed. One guy (at my lumber yard) thought it sounded like it had a lazy injector or was fuel restricted. He suggested changing the fuel filter. I haven't done that yet but I think I'm going to send the truck to a real Ford mechanic to see what he can find. thanks for the help and I'll post the result for those who are interested.
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From: Memphis, TN USA
Originally Posted by David Evans
I recently purchased a Cerry 1994 F-150 short box with a 302. It runs rough at idle up past 300 rpm.
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Joined: Dec 2003
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From: Memphis, TN USA
I really doubt it is a vacuum leak. As the throttle plate is opened the RPM should go up then the less vacuum required in the intake manifold.
Some vehicle that runs rough when revving the engine might have a partially clogged cat.
Some vehicle that runs rough when revving the engine might have a partially clogged cat.
Senior User
Joined: May 2001
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From: Kirkland WA
Try the TPS, I was just having a issue somewhat similar, so I pulled the TPS of of the Throttle Body, cleaned it up real good with some carb cleaner (not sure if that is advised or no) then threw it back in, worked like a charm. Also might be your ECTS, another coolant temp sensor on the lower intake manifold, screwed in up by the fuel injectors. Cheap part to replace anyway!
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I'll pass on the info on the throttle position sensor to my mechanic. He wants to check the timing. Something about it being electronically controlled and there being a "peg" or "post" (I think). anybody know about this?
